The ending is terrible and i hate it because Ash and Eiji both deserved so much better. But it actually kind of makes sense: after Ash was stabbed, i think he realized that violence and death will always be a part of his life and he can never completely escape it. So even if he could have survived (easily) and what he's done might be selfish - considering he probably knew how depressed Eiji was gonna get if he dies - it's still understandable... if you had a life like he did, wouldn't you feel paranoid all the time and wish for a way out ? Terrible ending, but - sadly - completely logical and understandable...
Geez, my heart hurts
shiT IS GOING DOWN DAMN